Our pharmaceutical laboratory has two moisture analyzers in use; one is Shimadzu MOC3u (MC-A), and the other is Mettler-Toledo HC103 (MC-B). A sample from the same batch was put on each instrument to determine its moisture content, and the two brands seem to have significantly different results: MC-A resulted in about 2.1% MC, and redrying resulted in a lower value at 1.5% MC MC-B, on the other hand, resulted in about 2.2% MC, but upon redrying resulted in almost the same value for MC at about 2.1% MC.
The settings for both instruments are set at 70°C for 8 minutes, and both are also recently calibrated and found to be within specifications.
Is there a specific reason why there is a significant difference in the results for the moisture content results? Which of the two results should we accept, and would the other result be invalid?